NEW YORK – The New York Giants usually treat the free agent market like a bug-infested swamp. They stay away.

Not heading into this summer’s training camp, though. With far too many holes on offense, defense and special teams during their 2013 debacle — an 0-6 start, 7-9 overall mark and no playoffs — the Giants were active in free agency from the start.

New York brought in 19 veteran free agents, 10 on offense. Running back Rashad Jennings is the presumptive starter, and any of three offensive line additions — Geoff Schwartz, John Jerry and J.D. Walton — could be a first-stringer.

The secondary was bolstered with cornerbacks Dominique Rodgers-Cromartie, Walter Thurmond and Zack Bowman.

For the Giants, it was an outright spending spree that also included defensive end Robert Ayers; linebacker Jameel McClain; kick returner Trindon Holliday; and old friend wide receiver Mario Manningham, who returns after a failed, injury-plagued stint in San Francisco.

“I think they made some great moves, some explosive moves, guys that can come in and contribute right away and help this team win.”

Watch for these things in the Giants’ preseason:

ELI’S ACCURACY: Eli Manning won’t play much in the exhibitions, although with the Giants scheduled for the Hall of Fame game, he’ll get a bit more action than in a normal preseason.

He needs to rediscover his sharpness after perhaps the worst season of his 10 in the NFL: a league-high 27 interceptions and a dismal 69.4 passer rating.

Manning has never been a great regular-season quarterback, but get him in big games — particularly the playoffs — and he’s dynamic.

He needs to kick some of the bad habits of 2013, particularly forcing throws and trying to do too much. And he’s operating in a new offense under Ben McAdoo, who replaces retired Kevin Gilbride as coordinator.

“We’ve spent a lot of time fundamentally … both footwork and everything from ball fakes, ball handling, to throwing accurately to dropping back,” quarterbacks coach Danny Langsdorf said. “There’s a little bit different footwork that we’re using, some of the routes that he’s used to, and we’re timing it up with the receivers, so there’s a little bit of fundamental work.

“But he’s a veteran guy and a pro that’s had success for a long time, so we’re not doing anything, (any) drastic changes.”

STALLED RUNNING GAME: The ground attack that for so long has complemented Manning is uncertain now. Jennings led Oakland with 733 yards and six TDs rushing last season, but he’s hardly a proven commodity.

David Wilson, the Giants’ top pick in 2012, is coming off neck surgery and will be watched carefully. Rookie Andre Williams and journeyman Peyton Hillis also are available.